The present invention relates to the formation of semiconductor devices.
During semiconductor wafer processing, features of the semiconductor device are defined in the wafer using well-known patterning and etching processes. In these processes, a photoresist (PR) material is deposited on the wafer and then is exposed to light filtered by a reticle. The reticle may be a transparent plate that is patterned with exemplary feature geometries that block light from propagating through the reticle.
After passing through the reticle, the light contacts the surface of the photoresist material. The light changes the chemical composition of the photoresist material such that a developer can remove a portion of the photoresist material. In the case of positive photoresist materials, the exposed regions are removed, and in the case of negative photoresist materials, the unexposed regions are removed. Thereafter, the wafer is etched to remove the underlying material from the areas that are no longer protected by the photoresist material, and thereby define the desired features in the wafer.
Various generations of photoresist are known. 193 nm and higher generation photoresist materials have been found to have problems being soft resulting in low etch selectivity, line edge roughness, striation, and line wiggling. Line edge roughness may be due to modifications to the photoresist mask, such as chemically etching away part of the photoresist mask or may be due to non-uniform polymer deposition. Non-uniform polymer deposition may be dependent on gases used, surface material polymer sticking coefficients, or resputtering. Line wiggling is believed to be related to stress caused by deposition of material on the photoresist mask. Non-uniform deposition on the photoresist mask may cause line wiggling stress.